Process for preparing thermoplastic resin composition with excellent HCFC resistance

Abstract

The present invention provides a process for preparing thermoplastic resin compositions having excellent HCFC resistance which comprises: a first step wherein 50 to 90 parts by weight of a monomer mixture of 50 to 80% by weight of a vinyl cyanide, 20 to 50% by weight of an aromatic vinyl compound and 5% by weight or less of an unsaturated carboxylic acid or esters thereof or a vinyl acetate are graft-polymerized in the presence of 10 to 50 parts by weight of a rubber latex and also in the presence of 0.001 to 2.0 parts by weight of a polymerization inhibitor to prepare a graft polymer(A); a second step wherein 100 parts by weight of a monomer mixture of 50 to 80% by weight of a vinyl cyanide, 20 to 50% by weight of an aromatic vinyl compound and 5% by weight or less of an unsaturated carboxylic acid or esters thereof are polymerized, while adding 2.0 parts by weight or less of a polymerization inhibitor to the mixture, to prepare a SAN copolymer(B); and a third step wherein the graft polymer(A) is mixed with the SAN copolymer(B) to form the composition wherein the rubber content in the composition falls within the range of 10 to 30% by weight of the composition. Also the thermoplastic resin composition can be provided by mixing the graft polymer(A) with a SAN copolymer(C) consisting of 25 to 40% by weight of a vinyl cyanide and 60 to 75% by weight of an aromatic vinyl compound to form the composition wherein the rubber content in the composition falls within the range of 10 to 30% by weight.

What is claimed is: 
     
       1. A process for preparing a thermoplastic resin composition having excellent HCFC resistance which comprises: a first step wherein 50 to 90 parts by weight of a monomer mixture of 50 to 80% by weight of a vinyl cyanide, 20 to 50% by weight of an aromatic vinyl compound and 5% by weight or less of an unsaturated carboxylic acid or esters thereof or a vinyl acetate are graft-polymerized in the presence of 10 to 50 parts by weight of a rubber latex and also in the presence of 0.001 to 2.0 parts by weight of a polymerization inhibitor to prepare a graft polymer(A) wherein the rubber latex comprises 20% by weight or less of the rubber particles having an average diameter of 0.07 to 0.15μ and 80 to 100% by weight of the rubber particles having an average diameter of 0.25 to 0.35μ;   a second step wherein 100 parts by weight of a monomer mixture of 50 to 80% by weight of a vinyl cyanide, 20 to 50% by weight of an aromatic vinyl compound and 5% by weight or less of an unsaturated carboxylic acid or esters thereof are polymerized, while adding 2.0 parts by weight or less of a polymerization inhibitor to the mixture, to prepare a SAN copolymer(B); and   a third step wherein the graft polymer(A) is mixed with the SAN copolymer(B) to form the composition wherein the rubber content in the composition falls within the range of 10 to 30% by weight of the composition.   
     
     
       2. A process for preparing a thermoplastic resin composition having excellent HCFC resistance, which comprises: graft-polymerizing 50 to 90 parts by weight of a monomer mixture of 50 to 80% by weight of a vinyl cyanide, 20 to 50% by weight of an aromatic vinyl compound and 5% by weight or less of an unsaturated carboxylic acid or esters thereof or a vinyl acetate in the presence of 10 to 50 parts by weight of a rubber latex and 0.001 to 2.0 parts by weight of a polymerization inhibitor to prepare a graft polymer(A) wherein the rubber latex comprises 20% by weight or less of the rubber particles having an average diameter of 0.07 to 0.15μ and 80 to 100% by weight of the rubber particles having an average diameter of 0.25 to 0.35μ; and, mixing the graft polymer(A) with a SAN copolymer(C) consisting of 25 to 40% by weight of a vinyl cyanide and 60 to 75% by weight of an aromatic vinyl compound which is prepared by mass-polymerization thereof, to form the composition, wherein the rubber content in the composition falls within the range of 10 to 30% by weight of the composition. 
     
     
       3. The process of claim 1 wherein the rubber latex has a gel content of 70 to 90% by weight. 
     
     
       4. The process of claim 1 or 2 wherein the polymerization inhibitor is selected from the group consisting of: p-t-butylcatechol, α-nitroso-β-naphthol, di-t-amylhydroquinone, dinitrobenzenthiol, dinitrophenylbenzothiazyl sulfide, sodium hydrosulfide, tetramethylthiuram disulfide, tetramethylthiuramide sulfide, dinitrophenylpyridinium chloride, sodium dimethyldithiocarbamate, potassium dimethyldithiocarbamate, p-nitrosomethylaniline, tetraethylenepentaamine, bis(p-hydroxynaphthyl)amine, nitric oxide, hydroxynaphthylamine, phenylhydrazine and bis-(p-hydroxyphenyl)amine. 
     
     
       5. The process of claim 1 or 2 wherein the vinyl cyanide is acrylonitrile or methacrylonitrile. 
     
     
       6. The process of claim 1 or 2 wherein the aromatic vinyl compound is styrene, α-methylstyrene or vinyltoluene. 
     
     
       7. The process of claim 1 or 2 wherein the unsaturated carboxylic acid or ester thereof is acrylic or methacrylic acid or methyl, ethyl, propyl, n-butyl or i-butyl ester thereof.